Protective covers

ABSTRACT

An enhanced protective cover includes a top and bottom textile layer and an air permeable, moisture-vapor-transmissive, expanded polytetrafluoroethylene membrane layer located between the two textile layers. The cover exhibits an MVTR rating of at least 4000 g/m 2 /day. The protective cover also includes a top layer coating or fiber treatment of a nano-ceramic material designed to increase the durability of the cover and increase the resistance to abrasion and wear while also resisting environmental conditions including exposure to solar radiation, temperature and humidity. Alternatively, the upper layer of the protective cover may incorporate ceramic coated fibers or ceramic co-extruded fibers, or carbon nanotubes. The protective cover may also feature a fire resistant application. The top textile layer may also include a permanent, highly breathable and highly durable electro-static discharge feature added to the inside of the layer by laying down a carbon based printed pattern on the inside of the layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.No. 61/578,446 titled “Protected Covers And Related Fabrics” which wasfiled on Dec. 21, 2011, and is a continuation-in-part of U.S. patentapplication Ser. No. 11/482,105 filed on Jul. 7, 2006 and entitled“Protective Covers And Related Fabrics”, both of which are incorporatedherein fully by reference.

TECHNICAL FIELD

The present invention relates to enhanced properties for protectivecovers for equipment typically stored outdoors such as airplanes,vehicles, munitions, weapons and weapons systems, electrical equipmentand the like, and more particularly, to the construction of fabrics forsuch protective covers.

BACKGROUND INFORMATION

Protective covers are often used to protect equipment and parts in awide range of environmental conditions. Corrosion and oxidation are ofparticular concern, especially in connection with vehicles, airplanes,munitions, weapons and weapons systems and equipment with metal and/orelectronic components and the like.

Prior protective covers that address the problem of corrosion aredescribed in U.S. Pat. Nos. 6,833,334, 6,794,317 and 6,444,595. Many ofthese covers have been found to have fundamental weaknesses that cancreate a microclimate underneath the cover when in use. The covers havebeen found to be generally impermeable to or provide good resistance torain, snow, and offer good water repellency. They generally use amonolithic impermeable coating on one side of the outer fabric layer toprovide water resistance.

In recognition of the microclimates formed underneath the cover, as ahumid environment cools and condensation forms on the protectedequipment, some of the covers utilize a center layer made of superabsorbent fibers (typically made from super absorbent polymer—SAP). Whenthe SAP absorbs the condensation it can make the cover extremely heavywhen wet and then can freeze in place in a cold environment. Thetechnology also sometimes uses vapor corrosion inhibitors (VCI's thatleach out of the cover as moisture passes through the cover and candeposit itself on the equipment leaving a moist residue on the equipmentit is trying to protect.

Additionally, current technologies use UV stabilizers in the dyes usedto color the cover fabrics and although this offers some level ofdurability, the cover life is still generally in the range of 9-18months of effective working life.

There remains a need, however, for more effective covers that provideprotection and resistance to penetration of water, wind and sand andthat are especially effective with respect to the prevention or at leastminimization of oxidation and/or corrosion due to humidity build-uparound the covered objects. Additionally, prior art protective covershave been found to be damaged by abrasion and other environmentalfactors caused by windblown sand, other wind borne particles and UVsolar light and therefore, the ideal protective cover should be durableand able to resist abrasion and damage caused by wind, sand and othersubstances, as well as resist degradation caused by UV energy from thesun.

It is desirable that covers perform in use without degradation orfall-off in performance for an extended period of time, preferablygreater than 4+ years. The primary mode of failure of most covers foundin use today is a loss in mechanical strength that can be observed inthe formation of holes and tearing of the fabric. This loss in strengthand durability is the result of molecular weight loss of the basepolymer from which the fabric is made via continued exposure toultra-violet light.

Protective covers of the type described above are designed andengineered to protect key assets both military and industrial that aresubject to corrosion and or degradation from exposure to environmentalconditions such as rain, fog, snow, wind, relative humidity, ultravioletlight and general pollution such as air borne dust, sand, acid rain etc.Such assets could be military hardware, such as helicopters and armoredvehicles, or electronic components such as generators or generalordnance (small to large scale guns). Overall, cover technology by meansof air permeable fabrics are proven to offer suitable protection to theassets described.

In addition, occasionally applications occur where a cover is needed toprotect and cover explosive materials and or sensitive electronicequipment. Usually materials used to manufacture covers use insulative,synthetic materials, such as polyester or nylon or similar textile wovenor knitted fabrics. The risk of a static electrical charge build upoccurring via the on-off motion from the described material cover or acharge build up from in-use dynamic movement and flexing of the covercould cause catastrophic failure of the cover and the asset beingprotected.

Previously some concepts used to impart electrical conductivity orstatic dissipation properties to cover materials have been tried andevaluated. Most include the use of yarns or threads containing apercentage component of either a metallic (stainless steel or coppersulphate) or carbon to render the yarn and thus the woven or knittedfabric made from the yarn, electrically conductive. Fabrics have beenmade where the conductive fabric uses 100% electrically conductive yarnsor the electrically conductive yarns can be strategically woven orknitted in to the fabric by use of a grid/square pattern oruni-directional design. In each case the conductive yarns which arealways present on either outer surface of the cover can be exposed tothe environments described herein which in turn leads to the risk oflong term durability failure based upon UV exposure and abrasion damage.Further, the cost of imparting such yarns in the finished fabric can beexpensive and cost prohibitive.

In many such cover applications described above it is also necessary toprovide fire resistance characteristics to the protective covers due tothe explosive materials that require protection. This Fire Resistancefeature must be provided without impacting the covers air permeabilityand Moisture Vapor Transmission Rating (MVTR) characteristics, addingweight or impacting Electro-static discharge.

Therefore, what is needed is a fabric cover with a multi-layerconstruction that uses an outer fabric that is designed to be durable,water-repellant, conforming, and flexible to be shaped and formed toprotect the equipment against corrosion and/or oxidation degradation andpotential catastrophic failure caused by its exposure to a wide range ofenvironmental conditions. The cover should provide greater than 2 timesthe current life of a cover and meet the industry requirements ofgreater than 4+ years of life. Additionally, the cover should addressthe problem of corrosion by providing a level of relative humidity (RH)management and control while also providing an effective and durableelectrical conductive or electro-static dissipative (ESD) performancecharacteristics to the cover material. A preferred fabric cover shouldalso include Fire Resistance characteristics.

It is important to note that the present invention is not intended to belimited to a system or method which must satisfy one or more of anystated objects or features of the invention. It is also important tonote that the present invention is not limited to the preferred,exemplary, or primary embodiment(s) described herein. Modifications andsubstitutions by one of ordinary skill in the art are considered to bewithin the scope of the present invention.

SUMMARY

In accordance with an exemplary embodiment of this invention, thepresent invention includes a hydrophobic but air-permeable middle layerwhich prevents build-up of a microclimate and stabilizes the pressureunder the cover, while still providing the desired water resistanceperformance needed. An air permeable protective cover is provided thatis designed to prevent the ingress of moisture but, at the same time, toallow moisture vapor underneath the cover to readily pass through to theouter environment, thereby preventing humidity buildup and thus helpingto prevent or at least minimize oxidation and corrosion of the coveredobject caused by condensation of any moisture trapped in the air underthe cover.

In the underlying technology, the cover is composed of several laminatedlayers of different materials. The multiple layers include at least anouter textile layer, an intermediate film or membrane of ePTFE or othersimilar hydrophobic material having good air permeability andmoisture-vapor-transmission properties, and an inner textile layer thatfaces toward the object being covered. For specific applications, theePTFE membrane may be an air permeable, breathable, treated membranesuch as an eVENT® membrane available from BHA Technologies. An optionalfourth fabric layer between the outer layer and the film or membrane mayincorporate Super Absorbing Polymers (SAPs) to prevent reabsorption ofmoisture back through the cover.

Corrosion or other inhibitors, such as an anti-microbial to inhibitmold, may also be included in either the textile layers or the membraneitself. All of the various embodiments preferably take advantage ofmoisture-wicking materials as the laminate layers to help removemoisture vapor from the covered equipment. The various layers orlaminations are held together by adhesive or any other acceptable methodin order to achieve the required durability of the final product.

The protective covers described herein preferably have a Moisture VaporTransmission Rating (MVTR) of at least 4000 g/m²/day or more and an AirPermeability rating of 0.15 CFM, and wherein the multi-layer fabricsystem when assembled together or independently, can maintain a relativehumidity transmittance rate through the structure at or greater than0.20%/minute/cu.ft. or 0.05 grains of moisture/minute/cu.ft.

In all cases, the inner textile layer may have material such as siliconedots applied to the inner face thereof, so that contact between thecover and the object to be protected is minimized if not eliminated, andto thereby enhance the moisture vapor transmission away from the object.

Textiles suitable for the outer layer include woven, knit and non-wovenfabrics such as nylon plain weave and ripstop-fabrics, warp knitfabrics, woven Cordura® (a registered trademark of Invista) fabric,Nomex® and Kevlar® (both registered trademarks of Dupont) fabrics,including blends Taslan fabrics (70-160D) and equivalents.

Textiles suitable for the inner layer include woven, knit and non-wovenfabrics such as lightweight warp or circular knit fabrics using nylon,polyester, Nomex® and equivalent fabrics, spunbond nylon andequivalents.

Accordingly, in one aspect, the invention relates to a protective covercomprising a textile layer and an air permeable,moisture-vapor-transmissive, expanded polytetrafluoroethylene membranelayer attached to the textile layer, the cover having an MVTR of atleast 4000 g/m²/day.

In another aspect, the invention relates to a fabric for use inprotective covers, the fabric comprising at least three layers includingan outer woven, knit or non-woven fabric layer and an inner woven, knitor non-woven fabric layer, and a moisture-vapor transmissive, airpermeable and oleophobic expanded polytetrafluoroethylene membrane layerbetween the outer and inner layers; the fabric having an MVTR of atleast 4000 g/m²/day.

In the preferred embodiment of the present invention, the protectivecover features an additional protection. The enhancement provides newlevels of durability (resistance to abrasion and wear) as well as newlevels of resistance to environmental conditions including exposure tosolar radiation, temperature and humidity. The invention involvestreatments to fibers, yarns and/or fabrics that provide a higher surfacewear, and greatly improved durability to sunlight exposures.

In a first embodiment, a top coating of ceramic based material, acurable coating including metal or metal oxide pigments, fire resistantcomponents and/or UV absorbing components is applied to the outermostlayer. In another embodiment, the threads of the outer layer fabric maybe individually treated with such a protective coating, while in yetanother embodiment, if the threads of the fabric are extruded, aco-extruded protective coating may be applied directly to the threads.In yet another embodiment, carbon nanotube fibers may be utilized as orincorporated into (along with other fibers or threads) the outer layer.Each additional protection layer is designed to increase the durabilityof the cover material and protect the cover material from damage causedby wind, sand, and other debris as well as protect from solardegradation caused by UV light.

In another embodiment, a permanent, highly breathable and highly durableelectro-static discharge feature is added by laying down a carbon basedprinted pattern on the inside of the laminate, providing a dischargerate of 0.5 sec or greater (5000 volt) on the top and bottom of thelaminate without the potential degradation from UV or abrasion.

In another embodiment, a permanent and highly breathable FR feature isadded by utilizing a gas plasma treatment process to bond FR compound tofibers to achieve flame times of less than 2.0 sec and char lengths ofless than 2 inches (FED STD 191 test methods 5903)

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reading the following detailed description, takentogether with the drawings wherein:

FIG. 1 is a cross section through a laminated protective cover inaccordance with an exemplary embodiment of the invention;

FIG. 2 is a cross section similar to FIG. 1 but with an additionaltextile layer interposed between the inner and outer layers;

FIG. 3 is a cross section similar to FIG. 3 but with a plurality ofspacers applied to the exposed face of the inner layer;

FIG. 4 is a partial perspective view of a composite fabric for making aprotective cover in accordance with another embodiment of the presentinvention in which the outermost layer is constructed of treated fibersor yarns;

FIG. 5 is a partial perspective view of a protective cover in accordancewith the invention applied over a military weapon; and

FIG. 6 is a comparison of the relative humidity shift when using a priorart cover with the cover according to the present invention, shown overa 30 minute time span.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a protective cover 10 is composed of laminatedlayers of different materials. The protective cover can comprise a sheetof predetermined length and form and used to cover the intended objectas a tarp. In addition, the laminated material forming the protectivecover may be cut and sewn to fit more precisely a specific object oritem of equipment. The seams of this cut and sewn cover may also haveseams that are taped or otherwise covered with a compatible material orare welded, in either case so that the finished cover is durablywaterproof.

In the exemplary embodiment, at least three laminated layers areemployed. These layers include an outer textile fabric or face layer 12;an interior intermediate layer 14; and an inner textile layer 16. Theouter textile layer 12 may be composed of suitable woven or non-woventextiles. For example, the outer layer 12 may comprise a high tenacitynylon 6,6-ripstop face fabric available from Precision Fabrics Group,Inc. of Greensboro, N.C. This fabric is of 0.003-0.004 in. thicknesswith 120 warp ends and 120 filling picks, with an air permeability of80-120 cfm/sq. ft and a weight of 1.1-1.3 oz/yd². Suitable Nylon 6,6ripstock face fabric is also available from Mitsui Textiles of Japan.Another suitable material for the outer textile fabric layer 12 is a 160Denier Cordura® woven fabric such as Milliken Style 900496-4. The fabrichas a weight of 4.5 oz./sq. yd. and is available from Millken Fabrics ofSpartanburg, sc. Other suitable textiles include nylon Taslan 70 Denierfabrics, and high modulus woven polyester fabrics available from varioussuppliers. The outer fabric layer 12 may be appropriately treated to bedurably water-resistant. Available treatments include, for example, aTeflon® finish from Dupont or other similar finish from Invista or otherknown suppliers. The treatments bond to the individual fibers and do notform a continuous coating, maintaining breathability of the overallfabric and cover.

An interior intermediate layer 14 is provided in the form of ahydrophobic film or membrane with good air permeability andmoisture-vapor-transmission properties. In the exemplary embodiment,layer 14 is an expanded polytetrafluoroethylene (ePTFE) layer. Theexpansion of polytetrafluoroethylene opens billions of microscopic poresin the resulting film or membrane 14 to enhance air permeability andwater vapor transmission rate.

The ePTFE layer or membrane is also preferably treated to render itpermanently oleophobic, waterproof and hydrophobic. A treated membraneof this type is commercially available from BRA Technologies under thetrade name eVENT® Fabric. The oleophobic property of this membrane isparticularly beneficial in that equipment, particularly militaryequipment, is often sprayed with oil to minimize corrosion. The ePTFEmembrane so treated is rendered resistant to hydraulic fluid, dieselfuel, weapon lubricants and similar field chemicals. Instead of coatingthe membrane with polyurathene, eVent fabrics are treated with apatented hydrophobic polymer to achieve oleophobic properties. eVentfabric's oleophobic polymer is applied by means of a supercritical gastreatment, eliminating the use of solvents during the productionprocess. This new technology enables both the gas and polymer tocompletely penetrate the pores of the eVent fabric's membrane,encapsulating each and every fibril during treatment but maintainingopen the pores in the fabric thus maintain air permeability.

It is believed that the unique value that eVENT® or similar fabric withsimilar properties offers is its ability to eliminate moisturecondensation on the article covered while providing a completelywaterproof protection (resists liquid water penetration at pressure ashigh as 10 meters of hydrostatic head). Moisture condenses on thesurfaces of the equipment being covered if the protective cover cannot“breathe”. This happens due to environmental temperature swings duringthe storage.

For example, if an object is covered with a nonbreathable protectivecover and the environmental conditions are 25° C. temperature and 50%relative humidity, then a drop of ambient temperature by 12° C. woulddrive the relative humidity inside to over 100% and hence lead tocondensation. Utilizing an eVENT® type membrane would keep the relativehumidity inside equilibrated to the ambient conditions by allowing themoisture vapors under the fabric to escape out.

Moisture or condensation is the primary cause of the corrosion thatoccurs to items contained under the cover as the climate outside thecover changes. In a preferred embodiment, the cover allows forsufficient air permeability thereby allowing the humidity and pressurechanges caused by changed in environmental conditions to stabilize sothe risk of condensation forming under the cover and on the equipment orasset being protected is minimized.

FIG. 6 shows how a cover, manufactured according to the first embodimentof the present invention, allows the relative humidity to escape fromunder the cover. The cover enables the air to get to equilibrium faster,thereby reducing or eliminating the condensation under the cover. Asshown in FIG. 6, the prior art (standard technology) cover maintains therelative humidity level over a 30 minute time span. In contract, thecover of the present invention drastically reduces the relative humidityover the same 30 minute time span.

The existing technology claims the cover materials are breathable basedupon a measured moisture vapor transmission rate (MVTR) primarilyattributed to the monolithic or micro-porous polyurethane coatingapplied to the cover material. This means a higher pressure under thecover must be attained and condensation must occur and be absorbed intothe polyurethane layer before moisture will start to transfer throughthe cover. In the prior art, a wet system of moisture traps the humidityand creates a difference in pressure that leads to condensation andcorrosion of equipment.

The impact of air permeability on relative humidity (shown in FIG. 6)was determined using a test chamber, which was developed to evaluate thetechnology. To keep the experiment simple, the temperature inside thetest chamber was maintained at an equivalent temperature as outside thetest fixture at 82+/−2 deg.F. Also, the % RH (relative humidity) outsidethe test fixture was measured at a constant 48% RH. The conditions inthe test chamber are then developed (hot rod and water bath) to generatea constant RH of around 85+/−2% with the test sample sealed inside thechamber. The door to the chamber is then opened exposing the test sampleto the outside environment. The test area is approximately 1 square footof surface area and the size of the chamber is approximately 1.5 cubicfeet. With the sealed door now open, the data is taken by measuring thechange in relative humidity inside the chamber with a hygrometer. A testis taken every minute to help determine a rate of which the change in RHis occurring inside the chamber.

The management of relative humidity offered by the new invention iscompelling and can be measured several ways. First, the chart shows thecover material of the new invention allowing relative humidity to passthrough almost immediately. The curve of the chart shows the rate of RHchange is relatively linear in terms of time. The chart showsapproximately a 1% change in RH/minute/square foot. Over the same timeperiod, zero change in RH has occurred with the current/existingtechnology. The next stage is to quantify the level of relative humidityor moist air passing through the new invention. It is known what theweight of dry air is at 0.075 lbs/ft³. Using a psychometric chart we cancalculate the weight of moisture in the chamber at 85% relative humidityand also at 50% relative humidity and thus extrapolate the rate ingrains or grams of moisture being transferred through the new inventioncover material.

It is known the weight of 1 cubic foot or air at 68 F at 65% RH is 0.075lbs. Therefore, to measure the quantity or rate of moisture removed bythe new cover material using the test chamber discussed, the followingmathematical model is used. 1.5 cubic feet of chamber at 0.075×85%relative humidity. 1.5×0.075×133=14.96 grains of moisture in chamber.Comparatively 1.5×0.075×80=9.0 grains of moisture outside chamber. Thus14.96−9.0=5.96 grains moisture removed in 30 minutes. Thus 6/30=moistureremoval rate 0.2 grains moisture removed/minute. Thus actual covermaterial rate 0.2/1.5=0.12 grains of moisture/minute/cubic foot. Ormultiply by 27=3.25 grains of moisture removed/minute/cubic yard.

Returning now to the construction of the protective cover according to afirst embodiment of the invention, the inner textile layer 16 faces theobject to be covered, and it is therefore preferable that the exposedsurface 19 be smooth so as not to scratch covered equipment. Thistextile fabric layer 16 may be composed of woven, knit, and non-wovenfabrics such as lightweight tricot warp knits of polyester or nylon.Such materials include Style 1158 manufactured by Hornwood and availablefrom KTex of Wayne N.J., or Style #0862, a 100% semi-dull nylon 6,6 with52 courses and 42 wales and a weight of 0.9 oz./sq. yd., available fromSomerset Industries of Gloversville, N.Y. Also suitable are non-wovenspunbond nylon fabrics such as Cerex Advanced Fabrics Orion style #70having a weight of 0.7 oz./sq. yd. and a thickness of 6-7 mil.

Another suitable fabric is yellow Nexus® nonwoven polyester having aweight of 1-1.2 oz./yd², and a thickness of 0.008-0.012 in., alsoavailable from Precision Fabrics Group. The inner layer may also behydrophilic, either by treatment or choice of fibers and construction,helping to wick moisture away from the covered object and to spread themoisture laterally, facilitating the vapor transmission through thecover to the outside. The inner layer may also be rendered electricallyconductive by either weaving in of inherently conductive fibers or bytopical (i.e. coating, printing, etc.) treatment.

Referring now to FIG. 2, a second embodiment illustrates a cover 18 thatincludes an outer textile or face layer 20 similar to face layer 12,overlying an interior textile fabric layer 22 incorporatingsuper-absorbent polymers {SAPS). The textile fabric layer 22 ispreferably a suitable non-woven fabric enclosing the SAP's in anotherwise conventional fashion. The layer 22 in turn overlies an ePTFEfilm or membrane 24 similar to membrane 14 described in connection withFIG. 1. The inner layer 26 is a textile fabric that may be of a materialsimilar to inner textile layer 16 described hereinabove. Use of SAPs inthe intermediate fabric layer 22 minimizes the possibility ofreabsorption of moisture back into the space below the cover.

FIG. 3 illustrates a variation of the embodiment shown in FIG. 1. Assuch, the outer textile or face layer 28, intermediate membrane 30 andinner textile layer 32 are similar to the corresponding layers 12, 14and 16 described hereinabove in connection with FIG. 1. Here, however,the cover 26 also includes a plurality of silicone (or other suitablematerial) spacers or dots 34 applied to the exposed face 36 of the innerlayer 32. The “dots” 34 may be applied in any random or patternedconfiguration and serve to maintain a space between (or at leastminimize contact between) the object to be covered and the inner textilelayer 32.

With the above configurations, the laminated protective cover allowsmoisture to be expelled readily from the interior covered area throughthe laminated cover itself to the outside environment. In this regard,the cover fabric and cover itself preferably have an MVTR of at least4000 to about 8000 g/m²/day and as high as 14000 g/m²/day or more, perISO 15496 (inverted cup method). The cover thus provides environmentalprotection and resistance to penetration of water, wind and sand. Thecover may be especially useful in the prevention of corrosion duringtransportation of military vehicles or other equipment, and protectionfrom contamination by chemical and biological warfare agents.

In the specific comparative example below, an ePTFE laminate cover inaccordance with the invention is constructed of three layers including:(a) Nylon 6, 6 Ripstop face fabric available from Mitsui Textiles,Japan; (b) ePTFE membrane; and (c) Nexus® polyester spunlace, 30 g/m2,available from Precision Fabrics Group. The ePTFE laminate is availablefrom BHA Technologies, Inc. under the name eV5004-3L.

In one example, the following commonly used protective cover materialswere compared against the above ePTFE laminate: (1) Herculite® 90 CoatedCover Fabric available from Manart-Hirsch Co., Inc., NY; (2) Sunbrella®Marine Canvas Cover Fabric available from Great Lakes Fabrics Inc., MIas their product number 4630; and (3) Polyethylene shrink wrap (MarineBoat cover) available from Shrinkwrap International Inc., MI

Mild Steel corrosion coupons were obtained from Metal Samples Company,AL. Each coupon was 2″×1″× 1/16″ in dimension. Ten such coupons werewrapped in each of the four cover materials and left in an open parkinglot for a period of two weeks. At the end of two weeks, the condition ofthe coupons was evaluated for signs of rusting. They were graded on ascale of 1 to 5, with 1 indicating that none of the ten coupons werevisually rusted and 5 indicating that all ten coupons were visuallyrusted.

The results from this evaluation are given in the table below. Alsolisted is the moisture vapor transmission rate of each of the fourlaminates.

TABLE 1 Corrosion Rating (average of ten MVTR (ISO 15496, COVER MATERIALrepeats) inverted cup) Herculite ® 90 4.8 0 Sunbrella ® Marine 2.6 6,900 g/m²/day Canvas Polyethylene shrink 4.2 0 wrap (Marine Boatcover) ePTFE laminate 1.1 14,000 g/m²/day (eV5004-3L}

It is also within the scope of this invention to add a layer of air(gas) permeable insulation such as Primaloft® within the laminate 10,specifically under the membrane, to retain heat under the cover. Inaddition, a metal (e.g. aluminum) reflective coating may be applied tothe exposed inner face of the inner layer for reflecting heat and/or forits electrostatic dissipative properties.

Another variation includes the addition of a durable water repellantcoating to the individual fibers that are used to make up the exposedface of the outer textile layer. Since this is not a continuous coating“on” the outer surface of the exposed face, such a water repellantcoating results in little to no impact on air permeability of the entirecover material.

In the preferred embodiment of the present invention, the outer textilecover layer (12, 20 or 28) includes a further level of durability thatincreases the resistance to abrasion and wear from environmental factorssuch as wind, sand, and other debris as well as increased resistance toenvironmental conditions including exposure to solar radiation (UVrays), temperature and humidity as well as fire resistance. This furtherlevel of durability can be implemented in the following embodiments.Each of the following embodiments may be implemented alone or incombination to increase the durability and reduce the degradation of theprotective cover (10, 18 or 26).

In a first embodiment, a top coating (13, 21 or 29) can be applied to anupper surface (15, 23 or 31) of the outer layer (12, 20 or 28). The topcoating (13, 21 or 29) provides increased durability and UV resistance.The top coating (13, 21 or 29) may be laminated or otherwise applied tothe upper surface (15, 23 or 31) of the outer layer (12, 20 or 28). Thetop coating (13, 21 or 29) typically includes a ceramic material. Thetop coating (13, 21 or 29) is preferably perforated or needle punched toprovide small holes that allow for the protective cover (10, 18 or 26)to “breathe” and continue to provide air permeability. The top coatingis preferably a ceramic or nano-ceramic surface UV stabilizer coatingapplied to the outer (upper) surface (15, 23 or 31) of the outer layer(12, 20, or 28) of the fabric system to increase the cover's resistanceto UV light to greater than two times the functional life of the cover(greater than 4 years) and minimize loss in relative humidity andairflow movement through the fabric system.

Simulation testing for UV stability can be done in a laboratoryenvironment using a Xenon Arc exposure that closely simulates thewavelengths found in sunlight (short wavelengths around 280-320 nm).Under test conditions as stated in ASTM D-154, 1000 hours of exposurecan simulate 24 months of direct sunlight exposure. Current materialshave shown to have less than 30% of their original strength after 1000hours, while the ceramic top coating of this embodiment of the presentinvention shows greater than 75% retained strength after 1000 hours ofexposure.

In another embodiment, the top coating (13, 21 or 29) applied to theupper surface (15, 23 or 31) of the outer layer (12, 20 or 28) may beapplied as a gas plasma coating. The finishing process may furtherinclude the application of a curable coating including metal or metaloxide pigments, fire resistant components and/or UV-absorbingcomponents.

The top coating (13, 21 or 29) can be formulated from a variety ofpolymer systems including curable acrylic polymers, polyurethanes,silicon polymer systems, polyesters, polyamides, or other polymers thatcan be cured by exposure to ultraviolet light, heat, or polymerizationcatalysts. The top coating composition can include a variety of metalsand metal oxides, such as boron, boron oxides, calcium oxides, ironoxides, lithium salts, titanium dioxide, carbon nanotubes, ultrafinecarbon particles, carbon, silicon dioxide, ceramics, all patent class Cmaterials, microscopic glass beads such as Aerogel, and the like.Preferred materials are highly reflective to incident UV radiation oropaque to UV radiation.

In yet another embodiment, a top coating (13, 21 or 29) can be appliedto an upper surface (15, 23 or 31) of the outer layer (12, 20 or 28)using an airfoam technique. An airfoam finishing coating technique, suchas EvoTop™, made by DyStar, Inc., is applied to the upper surface (15,23 or 31) of the outer layer (12, 20 or 28) of the protective cover (10,18 or 26). The coating includes ceramic and/or other protective elementsas described above. Other means of coating the fabric using similarmaterials with similar compositions are contemplated and within thescope of the current invention. The application of the coating 13, 21 or29 via an airfoam technique leaves small openings that allow the coatingto “breathe” without the need to perform the additional step of needlepunching.

In a further embodiment, a technique can be used that coats eachindividual fiber used to construct the outer layer 12 a as shown in FIG.4. In this embodiment, there is not an actual coating layer 13, 21 or 29but rather, in this process, each individual fiber 42 that makes up thefabric material of the outer layer (12, 20 or 28) of the protectivecover 10, 18 or 26 is coated, possibly with ceramic or anotherprotective material or element, prior to constructing (weaving orknitting) the fabric material.

This process may be accomplished by making a yarn or thread that can beused to make fabrics that have the desired durability and resistance tosunlight and ultraviolet radiation by first coating and curing one yarnbundle, then wrapping the coated yarn bundle in another layer of yarn(s)to minimize the surface abrasion that may be present on the coated yarnand to then weave the multi-layer yarn into a fabric.

In a further embodiment, when using a material that includes fibers thatare extruded, a ceramic or other type of coating can be applied directlyto the fibers during the fiber extrusion process (coextruding thecoating onto the fiber).

In this embodiment, the fabric for the outer layer may be constructed byspinning a bicomponent yarn or thread, which is a yarn with two distinctmaterial regions, where the outer yarn layer is spun from a polymer thathas been compounded with fine particulates that can protect the innerfiber component from UV exposure. Very fine particles, especiallyparticles that are finer than 2 microns in diameter, and even morepreferably particles that have a mean diameter of 0.5 microns or lessare preferred. The bicomponent fibers can be melt spun or solution spunusing techniques that are known to those skilled in the art of fiberspinning. The bicomponent fibers can then be made into yarns that haveexcellent stability to sunlight and UV exposures and mechanicalabrasion, but which are less abrasive themselves than the yarns orfabrics made by the coating processes.

Polymers that are useful for such bicomponent fibers can includepolyamides, polyester, acrylic polymers, aramids, and other polymersknown to make strong durable fibers. Materials that are useful for thelayer containing particulates include metals, metal oxides, carbon,carbon nanotubes, opaque glassy materials, microscopic glass beads, andthe like.

In yet another embodiment, carbon nanotubes can be either incorporatedinto the outer layer (12, 20 or 28) of the protective cover (10, 18 or26), as described above, or carbon nanotube fibers can be used toactually construct the outer textile cover layer 12, 20 or 28.

Each of the embodiments described above are used in conjunction with amulti-layer cover to provide improved cover durability includingresistance to wear and abrasion and resistance to environmentalconditions including solar radiation, temperature and humidity. Theouter layer (12, 20 or 28) material generally includes a fabric outerlayer composed of high strength yarns made from polymer such as nylon,polyester or aramid. In addition to the outer layer, the compositeincludes a “breathable” middle or intermediate inner layer (14, 22 or30). This intermediate layer is preferably a polymeric membrane thatpermits high levels of moisture vapor transport. The breathable middlelayer can be composed of such materials as expandedpolytetrafluoroethylene, microporous polyurethane, or other materialsthat provide both moisture vapor transport and resistance to thepenetration of liquid water, acids, bases, oils, greases and salt spray.The multi-layer cover also includes a lightweight, flexible fabric innerlayer (16, 26 or 32). The inner surface layer may be made from open meshtricot knits made of polyester or similar fabric, which provides supportfor the middle layer during lamination and which provides a flexiblesubstrate for the entire cover that has minimal resistance to air ormoisture transport.

In each of these various embodiments, a fire retardant application canalso be included either as an additional coating or added to the varioustop level coatings (13, 21 or 29) or as part of one of the other layersof the cover. In certain cover applications there is the potential thatthe cover may become exposed to a combustible environment, where thereis a risk that the cover may support combustion and result in adangerous environment for the equipment being protected or the personsoperating/maintaining/guarding the equipment.

In order to enable the cover to have a fire retardant quality, anymaterials used (such as nylon and polyester), which support combustion,can be treated with a flame retardant topical treatment (such asavailable from Alexium Inc.) or conversely the cover can be made withmaterials that are inherently non-combustible, such as aramid,mod-acrylic or other non-combustible materials. When creating afire-resistant material it is critical that the material still remainsair permeable, lightweight and still fire-resistant.

Prior art covers would coat the material (nylon or polyester) of thecover with a bromide and phosphate coating, which does not allow for airpermeability. In a preferred embodiment of the present invention, thecover is treated with a FR (fire retardant) compound such as thatcompound manufactured by Alexium Inc. and provided by the Duro Companyof Fall River, Mass., which prevents oxygen from getting into the nylon,thereby preventing the nylon from burning. When the material of thecover is treated with this compound, the material will melt, but notburn due to the treatment and the bonding technique. Meanwhile, thetreated fabric remains breathable.

The Alexium brand product is unique in that is utilizes Reactive SurfaceTreatment (RST), utilizing microwave energy to direct a precursor'spolymerization onto the substrate's (fabric's) surface. It then uses agas plasma to introduce minute quantities of the chemical to bepermanently bonded to the fabric, providing unique new fire retardantfunctions to the fabric without adversely impacting the fabric'sinherent properties such as MVTR, Air permeability or overall weight.The Fire retardant chemistry is a new nano non-halogenated formulationthat gives the fabric the desired self-extinguishing, no drip and nomelt properties.

Additionally, carbon fibers, bundles or yarns may be used in theprotective cover (10, 18 or 26), which provides static dissipative orelectrostatic discharge (ESD) or anti-static characteristics. Manyobjects that are protected by covers need ESD protection, which is notprovided by prior art covers. There is the potential that the cover maybecome exposed to a build up of static electricity, which creates a riskthat the cover will support an electrical charge and result in adangerous environment for the equipment being protected (electronic orsoftware, etc.) and the persons operating the equipment. Therefore, itis preferred that the cover exhibit electro-static dissipatingproperties. The electro-static dissipating ESD component applied to themulti-layer fabric is generally and typically configured to give anobject made with the multi-layer fabric system, such as an enhancedperforming protective cover, an electro-static decay performance of lessthan 0.5 seconds for 5000 volts measured at both a top and bottomportion of said enhanced performing protective cover.

An additional feature of another embodiment of the invention istherefore to impart a cost effective and durable electrical conductiveor electro-static dissipative (ESD) performance to the cover materialusing a screen printing technology of an electrically conductive ink.The print lay-down of ink is critical to conductivity performance and inthe case of the overall concept of the present invention, preventingloss of air permeability of the cover.

In a preferred embodiment of the present invention, a lower surface (17,25, 33) of the outer layer (12, 20 or 28) of the cover is treated with aprinted carbon treatment or conversely can be made with a fabricmaterial that is produced with ESD yarns or fibers. When the lowersurface (17, 25, 33 or 35) of the outer layer (12, 20 or 28) is treatedwith carbon material. The surface can be entirely treated or morepreferably, partially treated, such as with a pattern. The placement ofthe carbon on the lower surface (17, 25 or 33) of the outer layer (12,20 or 28) is superior to the prior art usage of carbon on an uppersurface of the outer layer of the cover, because the carbon on the uppersurface is subject to breakage and degradation due to UV solarbreakdown.

To ensure protection of the conductive print and long term function, theprint is applied ONLY to the inside of the cover fabric laminate.Because the print/ink is a water based polyurethane compound with adurable carbon particle component, when the ink is applied to thefabric, there is no significant loss in air permeability. If the printis applied to the ePTFE. the very small pore sizes (0.03 microns) arefilled with the ink, blocking substantial but not all air flow. When thecarbon print is applied to the inside of the woven nylon face fabric,the print adheres to the large yarn fibers and as a result in the wovenfabric blocks very little air flow. Openings in the face fabric areorder of magnitude 500× larger. Thus with the membrane part of the covercontrolling the overall air permeability of the laminate the ink must beprinted on the fabric and not the membrane. Effective coverage to attainto meet static dissipation requirements is based upon the level ofcarbon in the ink and the surface area printed on to the fabric. Trialsdone to date that provide optimum discharge used a 15-20% print lay downin a diamond shape pattern with approximately 1.5-2.0 mm lines over a1.0-1.5 square centimeter area.

One compelling aspect of this feature of the invention is that eventhough the printed ink is located on the inside of the laminate, theporous nature of the various cover materials and laminate layers usedallow volume electrical conductivity through the fabric/layers and thusallow static dissipation through the fabric. Static dissipation orstatic decay test method Federal Standard 191A and 4046 and NFPA-99challenges the conductive material to provide decay of 5000 volts inless than 0.5 seconds usually less than 0.1 seconds.

Further testing has shown that the ESD printing on the inside of thecover laminate does not significantly impact air permeabilityperformance of the membrane and thus does not impact or reduce the levelof relative humidity transported through the laminate. A cover materialwith ESD printing as described by this feature of the invention canstill maintain greater than 1% relative humidity transfer/square foot ofsurface area/per minute.

It is contemplated and within the scope of the present invention thateach of the additional levels of durability described above can be usedindividually or in combination with one another. Each of theseembodiments can also be used in conjunction with each of the previouslydescribed covers, including but not limited to, the use ofsuper-absorbent polymers, a plurality of silicone spacers or dots 34, aswell as the use of various fabric combinations previously disclosed.

Some of the applications for these laminate fabrics are protectivecovers that are particularly useful in situations where there is needfor protection against dust, sand, rain, microbes and UV light exposure,while minimizing corrosion. For example: (a) Protective covers formilitary and civilian helicopters and other aircraft; (b) Protectivecovers for military ground vehicles; (c) Protective covers for groundaviation equipment; (d) Protective covers for shipboard equipment; (e)Boat covers; (f) Vehicle covers (e.g., motorcycles, automobiles, etc.);(g) Military Tank hatch covers; and (h) Personal arms protective covers.

FIG. 5 illustrates one of many applications for the protective covers asdescribed herein. Specifically, a cover 38 is shown in place, covering amilitary weapon 40.

Composite fabric systems within the scope of the present invention couldinclude additional layers, selected to provide specific new attributesto the system and within the composite. Such systems might include oneor more layers to reduce sound transmission. Another would be to includea metal or metallized film layer that would reflect heat or dissipatesstatic or provide EMI shielding. Another type of layer that could beincluded might include materials designed to absorb particular parts ofthe electromagnetic spectrum, such as infrared radiation to reduce IRsignal or detection, radio signals or other means of detection. Yetanother type of layer could be included to degrade biological orchemical toxins.

Providing additional insulation value is another example of aparticularly useful additional composite layer. A preferred compositelayer for retaining heat while maintaining composite moisture vaportransport would be to include a gas permeable insulating layer such asPrimaloft® under the permeable membrane layer. Such a system wouldenable maintaining a warm environment within a shelter or cover whileallowing moisture to escape.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. Modifications and substitutions by one ofordinary skill in the art are considered to be within the scope of thepresent invention which is not to be limited except by the allowedclaims and their legal equivalents.

The invention claimed is:
 1. A protective cover comprising a multi-layerfabric system, said multi-layer fabric system comprising: a multi-layerfabric including an outer layer having an exterior facing surface and aninterior facing surface, wherein said exterior facing surface is treatedwith a ceramic based UV stabilizer coating; and said multi-layer fabricsystem having an electro-static dissipating (ESD) component and a flameretardant component applied to one or more layers of said multi-layerfabric, said one or more layers of said multi-layer fabric cooperatingto provide a relative humidity transmittance rate through themulti-layer fabric system at or greater than 0.20%/minute/cu.ft. or 0.05grains of moisture/minute/cu.ft.
 2. The multi-layer fabric system ofclaim 1 wherein said multi-layer fabric is a three layer structurecomprised of an oleo-phobic and hydrophobic treated woven or nonwovenouter layer, a micro-porous film as a second or middle layer and aoleo-phobic or hydrophobic woven, nonwoven or knit third/inner layer. 3.The multi-layer fabric system of claim 2 wherein the outer layer and theinner layer are adhesively bonded or laminated to either side of themiddle film layer.
 4. The multi-layer fabric system of claim 1 whereinthe ceramic surface UV stabilizer coating is applied to the exteriorfacing surface of the outer layer of the fabric system by means of aporous foam coating process.
 5. The multi-layer fabric system of claim 1wherein said electro-static dissipating ESD component compriseselectro-static dissipating carbon ink printed on at least a portion ofsaid interior facing surface of the outer layer of said multi-layerfabric.
 6. The multi-layer fabric system of claim 2, wherein the ESDcomponent is provided using 1 to 100% carbon based or metallic basedyarns or threads woven or knitted in at least one of the outer or innerlayers of the multi-layer fabric system.
 7. The multi-layer fabricsystem of claim 2, wherein the ESD component is provided using a 1 to100% carbon based or metallic based compound or fibril component mixedinto the micro-porous middle layer of the multi-layer fabric system. 8.The multi-layer fabric system of claim 1 wherein the flame retardantcomponent is provided either from fire retardant treatments applied toindividual layers or from fire retardant treatments applied to theassembled multi-layer fabric system by means of wet impregnation, diptreatment or by means of plasma fire retardant and microwave or apolymer deposition process.
 9. The multi-layer fabric system of claim 1wherein the micro-porous middle film layer is selected from the group offilm materials consisting of polyethylene, polyurethane and ePTFE(expanded polytetrafluoroethylene) materials.
 10. A multi-layer fabricsystem, the multi-layer fabric system comprising: an outer layer havingan upper surface and a lower surface, wherein said lower surface of saidouter layer is printed with a carbon containing material in at least apattern, and wherein said upper surface includes a ceramic based UVstabilizer material, and wherein at least said upper surface of saidouter layer is treated with a flame retardant treatment; an innertextile layer; and at least one air permeable and moisture-vaportransmissive intermediate layer, the at least one intermediate layerlocated between the outer layer and the inner textile layer, whereineach of said outer, inner and intermediate layers air permeable andmoisture-vapor transmissive, and wherein said multi-layer fabric systemprovides a relative humidity transmittance rate through the multi-layerfabric system at or greater than 0.20%/minute/cu.ft. or 0.05 grains ofmoisture/minute/cu.ft.
 11. A composite multi-layer fabric system, thecomposite multi-layer fabric system comprising: an outer layer with anupper surface and a lower surface, wherein said outer layer is airpermeable and moisture-vapor transmissive and wherein said lower surfaceof said outer layer is printed with a carbon containing material in atleast a pattern, and wherein said upper surface of said outer layer istreated with a flame retardant topical treatment; an inner textilelayer; and at least one air permeable and moisture-vapor transmissiveintermediate layer, the at least one intermediate layer located betweenthe outer layer and the inner textile layer.
 12. The multi-layer fabricsystem of claim 2, wherein said outer and said inner layers are textilefabric layers.